In atomic absorption spectroscopy, the measurement of the absorption of a radiation beam at a characteristic resonant spectral line for a particular element yields a measure of the concentration of that element in an original sample solution. Presently, one of the most common techniques for atomizing an element for purposes of the absorption measurement is by introducing a liquid sample solution of the element of interest into a gas burner wherein droplets of the solution are vaporized and the elements ultimately atomized, so as to form in the path of the apparatus radiation beam, a substantial quantity of the element of interest in its atomic state. A samle light beam, which originates from a line-emitting light source, and which includes a resonance line of the element to be measured, is directed through the flame. The desired element in the sample absorbs the resonance lines characteristic of the element and the emerging light beam is directed to a monochromator and thence to a detector which measures the degree to which the desired element absorbs the resonance lines of the sample beam. This absorption degree represents the amount of desired element in the sample substance.
For satisfactory operation of flame atomic absorption spectrophotometers, it is usually necessary to employ highly combustible mixtures of gases, such as mixtures of acetylene gas with an oxidant such as air or nitrous oxide.
In order to assure a quiet flame, the preferred practice is to supply an excess of the liquid sample solution over the amount which can be vaporized in order that larger droplets, which would result in a noisy flame, can be discarded. This excess of the sample solution must be drained away safely so that the burner does not become flooded with the excess liquid sample solution.
One of the potential hazards in the operation of such a system is that the combustible mixture of gases may accumulate in a liquid drain trap which is connected to receive the excess of the liquid sample solution which is drained from the burner, and that the accumulated gases in the liquid drain trap may later explode.
In order to avoid this occurrence, it is important that the end of the liquid drain line which carries excess solvent into the drain trap must be covered with liquid in the drain trap container so as to thereby restrict the flow of the explosive mixture of gases from the burner into the drain trap container.
Previously, it has been necessary to rely upon the operator to be sure that the liquid level in the drain trap is high enough to cover the lower end of the drain line, or to provide a float switch interlock to shut the system down if the liquid goes below a level which will cover the lower end of the drain line. However, both arrangements have shortcomings. Relying upon the operator is generally not considered safe, and the float switch arrangement has been found to be expensive, and may not be as reliable as desired.
Accordingly, it is an important object of the present invention to provide an atomic absorption spectrophotometer having an improved drain trap interlock which is lower in cost than prior interlocks.
It is another important object of the present invention to provide an atomic absorption spectrophotometer having an improved drain trap interlock which is more reliable than prior interlocks.
Further objects and advantages will be apparent from the following description and the accompanying drawings.